Fractional distillation



Jall- 26, 1932- c. w. wATsoN ET AL. 1,842,436

FRACTIONAL DI STILLATION Original Filed March 11,1924

Patented Jan. ze, 41932 CLAUDE 'W'. WATSON AND PERCY C. KEITH, IB/OF PORT ARTHUR,TES, ASSGNRS, Y MESNE ASSIGNMENTS, T O THE TEXAS COMPANY, OF MEW 'Yltly E'. Y., A

CORPORATION 'OF DELAWARE Application filed. March 11, 1924, Serial No. $923,375. enewed Novemher a, tatu.

rlhis invention relates to the fractionation of fluids and is adapted generallyfor the separation of fluids containing constituents of' different boiling points into particular frac tions desired.

In Conventional methods ofpfractionating it is common lpractice to provide a column or tower within whichfvapors and liquid are in counter current passage, a nal vapor Aproduct being taken olf at the upper end of the tower and a final liquid condensate being collected at the bottom of the tower. It is common to introduce the fluid to be fractionated into `the bottom pf the tower so that it comes in direct `contact with the liquid collected therein, Such a method of operation has the disadvantage that the liquid withdrawn from the tower will contain quantities of the lighter fractions which should properly be contained in the vapor which is i removed from the tower, since this liquid is in equilibrium with theA vapor evolved from it .and ywith the entering liuidsit is sought to fractionate.

Our invention contemplates an improvement in fractionating operations of such na,-` ture that it is possible to obtain, and removel our invention the'uid to be fractionated is.

brought into heat exchange relation, but not in direct Contact or equilibrium, with the final liquid condensate collected in the fractionat 'ing device so that the heat of the incoming i fluid is utilized to vaporize the lighter fractions in the i-indensate. Thus we provide a fractionating Zone in'which vapors and liquids are in counter current passage. 'llhe liquid collected from thefractionating zone is withdrawn and brought into heat exchange relation with the iiuid to be fractionated `whereby the withdrawn liquid is heated and vaporized to agreater or less extent. The heated liquid is thenutilized in suchv a manner as to create a current of upwardly rising va pors which passes into the fractionating none. rlhe fluid to be fractionated, after having thus been brought into heat exchange relation but not in equilibrium) with the liquid eendensate, is discharged into the fractionating zone at a predetermined point therein. t

Animportant' feature of the invention resides in the maintenance of the final liquid condensate collected in the fraetionating apparatus at a temperature in excess of that of the entering Huids, without the use of steam or other extraneous heating means. By bringing liquid condensate obtained from the fractionating zone into heat exchange relation with the heated Huids to he fractionated, prior. to the introduction of saine into the fractionu ating zone, and then introducing the liquid thus heated into the final. condensate collected, this final liquid pool may be maintained at a vtemperature in excess of that of the entering' charge or of that of any other point of the fractionating apparatus. The heated vapor rising from this pool and passing into the' fractionating zone insures a heat current through the zone such that maximum fractionation may be eii'ected. ln other words, the liquid reuxing through the zone is met with a current of vapor such that the desired revaporizations will occur There is a ternperature gradient through the fractionating zonel so that'i'efluxing liquid will in passage continually come in contact with Azones of in! creasing temperature.. ,eind since the final condensate is maintained at a temperature in excess of that of any point in the fraction-' ating zone and at the same time is not in equilibrium with the entering charge this liquid will contain the minimum quantity of lighter components. t

As the invention has a special lield of usefulness in connection with the distillation and fractionation of hydrocarbons, such as crude petroleum and the various products thereof, it will be described herein in detail with particular reference to the distillation of hydrocarbon oils.

The invention is best described by reference to specific apparatus constituting an example thereof and for the purpose of fully tit) disclosing the invention reference will now be had to the accompanying drawing which shows a diagrammatic elevation ot' an apparatus constructed in accordance with the in' vention and constituting an embodiment thereof.

The apparatus thuslillustrated comprises an exchanger A and a fractionating apparatus B. The fluid to be fractionated is admitted through a pipe 10. This pipe may constitute, for example, a vapor line extending from a still wherein hydrocarbon oils are being vaporized so that the material in the line consists essentially of hydrocarbon vapors. 'lhe still may be operated at normal pressure, under a vacuum or diminished pressure, or under a superatmospheric pres sure, and simple distillation or destructive distillation or cracking may be carried on in the still. Thematerial to be fractionated may likewise comprise mixed vapors and liquid. Thus, for example, the fluid may consist of the heated products obtained from a stripping still, tubular or otherwise, 0perated for example under superatmospheric pressure. It is to be understood that the invention does not relate per se tothe method of originally heating the Vmaterial' to be fractionated and that the invention has in view `the treatment of fluids, from whatever source derived, consisting of components in the vapor or gaseous state, or of constltuents comprislng a mixture of liquids and vapors or changer A. The heat exchanger is arrangedr for the passage of separate fluids in heat exchange relation with each other and may be of any particular design desired. As shown, the exchanger comprises concentric pipes 11 and 12 .arranged in the form of a coil. The pipe 410 may communicate with either element of the exchanger, that is, with either the inner or outer channel; it isv shown as communicating with the outer coil 11.'

The fractionating apparatus B is preferably arranged in the form of a rectifying column or tower 13 and to obtain best results should be provided with insulation such as 14. The chamber 13 is provided with suitable means for effecting proper contact between vapors and liquid so as to produce repeated distillations and condensations whereby fractionation may be effected. The chamber is shown as being provided with contactl material 15. Any of the conventional contact arrangements common in rectifying and fractionating equipment may be used, such as bubble trays or comparti ments, broken stone or other fragmentary mater1al, various types of fractionating rings and other contact elements, etc.

The tractionating apparatus is provided at the bottom with a space for the collection of a pool 16 which constitutes the final liquid condensate obtained in the apparatus. Intermediate the fractionating zone proper, denoted by the contact material 15, and the pool 16 means is provided, as at 17, for collecting a pool of liquid condensate derived from the fractionating zone. Means is provided at 18 to permit the passage of vapors from the space 16 into the fractionating zone 15. A pump 19 has an inlet line 20 communicating with the pool 17 and an outlet pipe 21 which terminates in the heat exchanger coil 12. A pipe extends from the coil 12 to a point below the pool 17 so as to .discharge fluid into the pool 16. Liquid from the pool 17 may thus be drawn ofl' and brought into heat cxchange relation with the fluid which is passed through the coil 11 and the heated fluid conducted by the pipe 22 lto the pool 16. As indicated in the drawing, the fluids flow through the heat exchange coils 11 and 12 in counter current.

A pipe 23 is provided to conduct fluid from the pipe 11l to the fractionating zone. As is illustrated, the pipe 23 preferably terminates at an intermediate point in the fractionating zone.

A vapor line 24 is provided to remove va- -pors from the tower. It is shown as terminating'in a condenser coil 25 provided with an outlet 26.

The fractionating apparatus is provided with suitable means for creating a reflux liquid adapted to pass down through the fractionating zone in counter current to the flow of vapors. Various means may be used to accomplish this object. Thus the upper portion of the tower may be provided with a cooling coil to create sufficient cooling to initiate the formation of reflux liquid or a reflux condenser maybe inserted in the vapor line 24 with a backtrap line for refluxing liquid to the upper part of the chamber. In the arrangement shown a pipe 27 is provided for admitting a cooling liquid to the upper portion of the fractionating zone and a pump 28 for handling the cooling liquid is shown as having an inlet pipe 29 communicating with pipe 26 so that a portion of the condensate from the coil 25 may be utilized as a cooling or refluxing medium.

A pipe 30 which, if desired, may extend to a cooling coil 31 is provided for withdrawing liquid from the pool 16.

In practicing the invention the heated fluid to be fractionated is passed through a pipe 10 and thence through the exchanger A in counter current heat exchange with the liquid drawn oft1 from the pool 17. The fluid to be fractionated is thus cooled to a certain extent while the material withdrawn from the fractionating apparatus is heated. The fluid it is desired to fractionate is then admitted to fhe fractionating zone wherein the counter currents of vapor and liquid produce successive redistillations and condensations with the-resultant accumulation of liquid in the pool 17. This liquid is withdrawn, as stated, brought into heat exchange relation but not into equilibrium with the incoming heated fluids and then conducted to the pool 16. Any o'tthe lighter components which properly belong in the vapors removed through the vapor line 24 but which are held in solution in4 the liquid removed from the pool 17' are vaporized by means of the heat received lin passage through the exchanger A and upon being released into the chamber at the bottom ot the' ractionating tower the vapors pass oil' trom the pool 16. A current of vapors is thus initiated which passes upwardly into the fraction'ating zone supplying heat thereto. v

lt is apparent that when the fluid to be fractionated is admitted to the fractionating zone that the upwardly rising vapors come in contact with the reflux liquid flowing downwardly therein so that the vapor which passes throughmt-he vapor line 24: and is collected as a condensate inthe condenser 25 is thus substantially tree :from heavy ends or constituents of higher boiling point than that desired. The liquid passing downwardly through the apparatus is continually met with currents of vapor of progressively increasing temperature and the condensate col.-

`lected from the tractionating zone in the pool 17 by being brought into heat exchange relation with the heated vapors or other fluid being admitted to the fractionating apparatus, but not coming intoy direct' contact or equilibrium therewith, is substantially tree' from' the lighter constituents so that the final liquid collected in the pool 1 6 and withdrawn through the pipe 30 contains none, or at least a minimum, of the lighter bodies,` that is,

those constituentsl which properly belong in the vapors passing out through the line/24.

By means ot our invention it is comparatively easy to take off from a 'fractionating appara- 'tus an overhead distillate having an end boiling point lower than that ot' the initial boiling point of the bottoms or final liquid condensate withdrawn from the apparatus.

Although the preferred embodiment of the invention has been vset forth in. connection with apparatus having a particular construction and arrangement of parts and mode of operation. it is obvious that various changes and modiiications may be made therein, while securing to a greater or less extent some or all ot the benefits of the invention, without departing from the spirit and scope thereof.

Therefore, only such limitations should be imposed as are indicated in the appended claims.

Whatwe claim' is:

' l. Apparatus 'for tractionating fluids comprising a tractionating' chamber, a heat exchange element adapted for the tiow of separate fluids in counter current through separate channels in heat exchange relation to each other, means 'for admitting fluid to one of the channels ot the heat exchanger, means for conducting luid from said channel of the heat exchanger to a predetermined mid-point in said tractionating chamber, means for withdrawing liquid at a lower point in said chamber and admitting it to the other channel of theheat exchanger and means for conducting liquid from said latter channel to a still lower portion of said fractionating chamber. i Y

' 2. Apparatus Jtor fractionating fluids comprising a chamber. means for admitting to thechamber fluid to be fractionated, means for collecting a pool ot condensate from the ractionating` chamber. means 'tor Ywithdrawtractionated to one ot said conduits, means for conducting the tluid from lsaid conduit to the fractionatiug apparatus. means for withdrawing liquid trom the tractionating apparatusat a predetermined point and conducting-same in a direction opposite to the How of said duid, through the other ot said conduits and means for returning the heated liquid to the 'tractionating apparatus at a lower oint. p 4. Themethod ot tractionating fluids that comprises admitting Huid to a tractionatingl chamber wherein it is subjected to fractional distillation. withdrawing liquid from said chamber at a point below that at which said Huid is admit-ted, passing the liquid thus withdrawn in heat exchange relation and in counter current with said Huid prior to its introduction to the fractionating chamber. and passing the liquid thereby heated to the bottom ot the iractionating chamber.

5. rlhe process of tractionating fluids that comprises maintaining a pool of condensate collected in the lower portion of a traction- 4 and imparting 'such' abstracted heat to the lower'pool, and then passing all the iiuid 'from which heat has been so abstracted directly'into the tractionating tower at a prcdetermined intermediate point thereof.

yln witness whereot we have hereunto set our hands this 29th day ot February, 1924.

' C. W. 'WATSN P. C. KEITH, JR.

CERTIFICATE 0F CORRECTN.

Patent No. l;842,436. amlai'y 26; i932.

CLAUDE w; WATSON ET AL.

it is hereby e'iiie thai error appesi-s in the printed specifcaem @i iii@ above numbered mima requiring @affection as follows: Page 3, line S8, ciaim 2, im "Huid" remi Eqinid; and Kimi ih@ Said Letters Fatemi @hamm be me@ wiiie this @affection Mmmm @im @im same may emiformto the recmai of iii@ ms@ in me Psiem @iw Signe@ andseied ibis 27th day yf-September, A. D. 1932.

M. J. Moore,

y(Seal) Acting Commissioner of Patents. 

